Shrub climate sensitivity and the heterogeneity of the greening of the tundra

灌木气候敏感性和苔原绿化的异质性

• 批准号: RGPIN-2018-04587
• 负责人: Boudreau, Stéphane
• 金额: $ 2.04万
• 依托单位: Université Laval
• 依托单位国家: 加拿大
• 项目类别: Discovery Grants Program - Individual
• 财政年份: 2019
• 资助国家: 加拿大
• 起止时间: 2019-01-01 至 2020-12-31
• 项目状态: 已结题
• 来源: https://www.nserc-crsng.gc.ca/ase-oro/Details-Detailles_eng.asp?id=682781
• 关键词: Shrub; climate; sensitivity; heterogeneity; greening

The greening of Arctic and Subarctic regions over the last decades has been mainly associated with the rapid expansion of erect shrub species. Observed throughout the circumpolar region, shrub expansion deeply alters the structure and function of tundra ecosystems by reducing overall albedo in terrestrial ecosystems, resulting in a positive feedback to climate change. Shrubs also affect patterns of snow deposition, accumulation and snowmelt and contribute to deepening the active layer and accelerating permafrost degradation. Shrub expansion is however highly heterogeneous throughout the Arctic and the Subarctic regions and the drivers of such heterogeneity are still poorly understood. While climatic drivers of erect shrub growth have been partially identified, recent advances in shrub dendrochronology suggest that shrub climate sensitivity is site- and species-specific, with evidence of higher sensitivity in Eurasia and in wetter regions. However, these findings are based on studies that rely on samples collected at different positions on shrub individuals (root collars or stems) and therefore, they did not consider the impacts of the multi-stem growth form of erect shrub species on their climate sensitivity. Differential climate sensitivity within a single individual might hamper analysis and interpretation of large dendrochronological datasets. ******Therefore, the long-term objectives of this research program aim to disentangle the effects of climatic, topographic and edaphic factors on the growth of shrub species and, by extension, on the heterogeneity of the greening trend observed in the tundra over the last decades. Over the next five years, my team will test the following research hypotheses: 1. The heterogeneity in the greening trend observed throughout northern North America results from the differential climate sensitivity of shrubs at various spatial scales; 2. The climate sensitivity of shrubs is closely associated with both edaphic and topographic variables; 3. The multi-stem growth form of erect shrub species influences their sensitivity to climate.******This research program linking shrub expansion, greening of the tundra and shrub climate sensitivity will generate results of significant interest not only for the scientific community but also for governmental agencies responsible for the development of the North. By determining if the greening trend heterogeneity is associated with differential shrub climate sensitivity, our results will feed the models that aim to predict vegetation changes over the next century and will contribute to the development of shrub dendrochronology by, at the very least, laying the foundations for standard sampling protocols. Through the different research projects, this program will contribute significantly to the training of Highly Qualified Personnel (2 Ph.D., 2 M.Sc. and 5 undergraduate students).

过去几十年来，北极和亚北极地区的绿化主要与直立灌木物种的快速扩张有关。在整个环极地区观测到，灌木扩张通过降低陆地生态系统的总体反照率，深刻地改变了冻土带生态系统的结构和功能，从而对气候变化产生正反馈。灌木还影响雪的沉积、积累和融雪的模式，并有助于加深活土层和加速永久冻土的退化。然而，在整个北极和亚北极地区，灌木扩张是高度异质性的，这种异质性的驱动因素仍然知之甚少。虽然直立灌木生长的气候驱动因素已被部分确定，但灌木年代学的最新进展表明，灌木的气候敏感性是地点和物种特异性的，有证据表明欧亚大陆和湿润地区的敏感性更高。然而，这些研究结果是基于在灌木个体（根颈或茎）不同位置采集的样本，因此没有考虑直立灌木物种多茎生长形式对其气候敏感性的影响。单个个体的不同气候敏感性可能会妨碍对大型树木年代学数据集的分析和解释。******因此，这项研究计划的长期目标是解开气候、地形和土壤因素对灌木物种生长的影响，并由此扩展到过去几十年在冻土带观察到的绿化趋势的异质性。在接下来的五年里，我的团队将测试以下研究假设：1。北美北部地区绿化趋势的异质性是由于灌木在不同空间尺度上的气候敏感性差异所致；2. 灌木的气候敏感性与土壤和地形变量密切相关；3. 直立灌木的多茎生长形式影响其对气候的敏感性。******这个将灌木扩张、苔原绿化和灌木气候敏感性联系起来的研究项目，不仅将为科学界带来重大利益，也将为负责北方发展的政府机构带来重大利益。通过确定绿化趋势异质性是否与不同灌木气候敏感性相关，我们的研究结果将为旨在预测下个世纪植被变化的模型提供依据，并将通过至少为标准采样方案奠定基础，为灌木年代学的发展做出贡献。通过不同的研究项目，该计划将为培养高素质人才（2名博士，2名硕士和5名本科生）做出重大贡献。